#!/usr/bin/env python3
# -*- coding:utf-8 -*-
__author__ = 'Jinyang Shao'

from socket import *
import os
import sys
import struct
import time
import select
import binascii

ICMP_ECHO_REQUEST = 8


def checksum(string):
    csum = 0
    countTo = (len(string) // 2) * 2
    count = 0
    while count < countTo:
        thisVal = ord(string[count+1]) * 256 + ord(string[count])
        csum = csum + thisVal
        csum = csum & 0xffffffff
        count = count + 2
    if countTo < len(string):
        csum = csum + ord(string[len(string) - 1])
        csum = csum & 0xffffffff
    csum = (csum >> 16) + (csum & 0xffff)
    csum = csum + (csum >> 16)
    answer = ~csum
    answer = answer & 0xffff
    answer = answer >> 8 | (answer << 8 & 0xff00)
    return answer


def receiveOnePing(mySocket, ID, timeout, timesend):
    timeLeft = timeout
    while 1:
        startedSelect = time.time()
        whatReady = select.select([mySocket], [], [], timeLeft)
        howLongInSelect = (time.time() - startedSelect)
        if whatReady[0] == []:  # Timeout
            return "Not ready. Request timed out."
        timeReceived = time.time()
        recPacket, addr = mySocket.recvfrom(1024)
        # Fill in start
        # Fetch the ICMP header from the IP packet
        icmp_header = recPacket[20:28]  # The ICMP header starts after bit 160 of the IP header
        type, code, checksum, p_id, sequence = struct.unpack('bbHHh', icmp_header)
        if p_id == ID:
            return timeReceived - timesend

        # Fill in end
        timeLeft = timeLeft - howLongInSelect
        if timeLeft <= 0:
            return "Request timed out."


def sendOnePing(mySocket, destAddr, ID):
    # Header is type (8), code (8), checksum (16), id (16), sequence (16)
    myChecksum = 0
    # Make a dummy header with a 0 checksum
    # struct -- Interpret strings as packed binary data
    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, myChecksum, ID, 1)
    data = struct.pack("d", time.time())
    # Calculate the checksum on the data and the dummy header.
    myChecksum = checksum(str(header + data))

    # Get the right checksum, and put in the header
    if sys.platform == 'darwin':
        # Convert 16-bit integers from host to network byte order
        myChecksum = htons(myChecksum) & 0xffff
    else:
        myChecksum = htons(myChecksum)

    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, myChecksum, ID, 1)
    packet = header + data

    mySocket.sendto(packet, (destAddr, 1))  # AF_INET address must be tuple, not str
    # Both LISTS and TUPLES consist of a number of objects
    # which can be referenced by their position number within the object.


def doOnePing(destAddr, timeout):
    icmp = getprotobyname("icmp")
    mySocket = socket(AF_INET, SOCK_RAW, icmp)
    myID = os.getpid() & 0xFFFF  # Return the current process i

    sendOnePing(mySocket, destAddr, myID)

    delay = receiveOnePing(mySocket, myID, timeout, time.time())

    mySocket.close()
    return delay


def ping(host, timeout=1):
    # timeout=1 means: If one second goes by without a reply from the server,
    # the client assumes that either the client's ping or the server's pong is lost
    dest = gethostbyname(host)
    print("Pinging " + dest + " using Python:")
    print("")
    # Send ping requests to a server separated by approximately one second
    while True:
        delay = doOnePing(dest, timeout)
        print(delay)
        time.sleep(1)  # one second
    return delay


ping("baidu.com")
